Looking to create a webpage which will compare the prices from different online shopping sites..

example
1) consider i have a list of 5 websites which sell items online...
if there is information about a PRODUCT A in MY site...
then it shud check if that PRODUCT A is being sold by any website in the list (1),
if yes then it should display its price....

im comfortable with wordpress, and kno how to insert and run PHP code, mysql queries.. [but jst a beginer in PHP]

have no idea on how to achieve this, so any help will be appreciated..